We registered how eight subjects used their remotely controlled black Venetian blinds in eight individual offices, every 15 min, over a period of 30 weeks. This also included measuring parameters such as the illuminance on the window, the illuminance on the VDU screen, the ambient temperature inside the room, the presence of the worker and the state of the artificial lighting. During the same period, we registered the position of the blinds in seven other offices fitted with manually controlled fabric blinds, through webcam pictures taken every 15 min. There was no further monitoring inside these offices. With the data collected, several hypotheses regarding the use of Venetian blinds in offices were tested. It appeared that office workers were consistent in the way they used their shading system, however it was difficult to draw general conclusions on blind usage. The type of control of the shading system also seemed to be important. Remotely controlled black Venetian blinds were used three times more often than manually controlled fabric blinds. In addition, most of the time users adjusted the tilt of the slats of the Venetian blinds downwards, towards the external ground. We also came to the conclusion that the higher the quality of the VDU screen (in terms of emitted luminance levels), the more likely a worker was to tolerate high levels of diffuse reflections on it, hence taking more advantage of the daylight available. (c) 2006 Elsevier B.V. All rights reserved.